Preparation of cis-1,4-dienes



United States Patent 3,441,627 PREPARATION OF CIS-1,4-DIENES WolfgangSchneider, Broadview Heights, Ohio, assignor tYoThe B, F. GoodrichCompany, a corporation of New o'rk No-Drawing. Filed July 6, 1965, Ser.No. 469,880 Int. Cl. C07c 11/12 US. Cl. 260680 4 Claims ABSTRACT OF THEDISCLOSURE Cis-l,4-dienes, which are useful third monomers in thepreparation of vulcanizable rubbers with ethylene and propylene, areobtained by reacting a 1,3-diene containing 4 to 6 carbon atoms withethylene in the presence of a catalyst consisting of an iron compound,an alkyl aluminum compound and an organic nitrogen compound.

This invention relates to an improved method for preparingcis-1,4-dienes.

1,4-hexadiene is used as a third monomer in preparing vulcanizablerubbers of ethylene and propylene terpolymers. In preparing1,4-hexadiene by known methods, a mixture of cisand trans-isomers isobtained. It is desirable to have an all cis-1,4hexadiene available forpreparing vulcanizable ethylene-propylene rubbers. At presentcis-1,4-hexadiene is an expensive monomer since it first must beseparated from the trans-isomer and the trans-isomer then discarded,which represents a loss of costly raw materials.

This invention now provides an economical method for readily preparing1,4-hexadiene, methyl-1,4-hexadienes and 1,4-heptadiene of predominantlycis-structure in high yields to the exclusion of the trans-structure,which comprises reacting a 1,3-diene such as butadiene, isoprene orpiperylene and ethylene in the presence of a catalyst which is formed byreacting together a reducible iron compound with a reducing agent suchas alkali, alkaline earth and aluminum metals, hydrides, alkoxides andalkyls thereof, and an organic compound which is an electron donor inthis reaction for the transition metal, which compounds are describedhereinafter.

The reducible iron compound may be any dior trivalent compound of ironwhich is readily reduced by an alkyl metal compound. Useful ironcompounds include the chlorides, bromides, sulfates, hydroxides,nitrates, oxalates and other salts of inorganic and organic acids.Organic compounds useful in the process are iron chelates in which theiron is attached to two functional groups of a, molecule by a mainvalence bond and coordinately, for example, iron acetylacetonate. Theiron compounds are preferably used in an anhydrous state.

The reducing agents, which may be I-A, IIA, or IIIA metals, hydrides, oralkyl derivatives thereof, are usually organo-metallic compounds,including lithium alkyls, beryllium alkyls, aluminum alkyls, and thelike, mixtures of alkali, alkaline earth and aluminum metals and alkylhalides, and alkoxides. More usually employed are aluminum alkyls, alkylalkoxides, hydrides and aluminum alkyl halides having the formula R Alor R AlX wherein R is an alkyl group containing 1 to 12 carbon atoms,preferably 2 to 8, X is an alkoxyl, hydride or a halogen atom, and x is1 or 2, y is 1 or 2, and x+y=3. Typical compounds include triethylaluminum, tributyl aluminum, triisobutyl aluminum, diethyl aluminumchloride, dibutyl aluminum chloride, ethyl aluminum dichloride, diethylaluminum ethoxide, propyl aluminum dichloride, diisobutyl aluminumchloride, and mixtures thereof. Other useful organo-metallic compoundsinclude zinc diethyl, triisobutyl borane, and Grignard reagents "ice asethyl magnesium bromide and other alkyl magnesium halides, also wherethe alkyl group contains 1 to 12 carbon atoms. b

In addition to the organo-metallic compounds, metals which have areducing action on dior trivalent iron compounds can be used as reducingagents, for example metals belonging to I-A, lI-A or III-A or theLanthanide group of the Periodic Table. Of these metals it is preferredto use lithium, sodium, potassium, magnesium, calcium, strontium,beryllium, barium, aluminum, gallium, indium, and cerium. They areconveniently used in a condition in which they have a large surface, forexample, in the form of chips or powder. Obviously, alloys or mixturesof two of the said metals may also be used. In many cases the use of analkyl or aryl halide or a halide of an element of group lI-A or IIIAalong with the metal is of advantage. Of the halides, the bromides andchlorides are preferred. Examples of suitable compounds are: allylchloride and bromide, ethyl chloride and bromide, boron trichloride,aluminum chloride, and the like.

The electron donors suitable for use for preparing the active catalystsinclude compounds which contain linking electron pairs, such as organiccompounds of an element of groups V-A and Vl-A of the Periodic Tableincluding nitrogen, phosphorous, arsenic, antimony, sulfur, and oxygen.A preferred group of compounds of group VA are those containing nitrogenor phosphorous present in the compound in a trivalent state and whichcontain alkyl or aryl radicals and which may contain other substituentsin an ortho, para, or meta position to the bridge. Typical of suchcompounds are triphenyl phosphine, triphenyl phosphite, triphenylstibine, triethylamine, triphenylamine, trimethylene diamine,triethylene dia'mine, pyridine, piperidine, morpholine, acrylonitrile,benzonitrile, and acetamide. A useful group of compounds containing VIAelements are diphenyl ether, diphenylsulfone, butadiene cyclic sulfoneand isoprene cyclic sulfone. Another group of electron donors which maybe used in the process of invention include aromatic halogen compoundsincluding chlorob enzene, dichlorobenzene, orthoandmeta-chlorobenzonitrile and trichloroaniline. Preferred are alkyl aminescontaining 2 to 12 carbon atoms, acrylonitrile and benzonitrile.

In the preparation of the catalyst, the iron compound and reducing agentare reacted together in the presence of a 1,3-diene. The electron donormay be added during this reaction or thereafter. Suitable 1,3-dienes arebutadime-1,3, isoprene and piperylene.

The reaction may be conducted over a Wide range of temperatures andpressures. Normally, the reaction is conducted at a temperature aboveroom temperature, that is, about 25 C. to temperatures as high as about250 C. More preferably, the reactions are conducted at temperatures inthe range of about 50 C. to 150 C. At higher temperatures, the catalystdecomposes, and undesirable by-products are formed.

The reaction may be carried out at atmospheric pressure, but usually isat higher pressure. This is determined by the vapor pressure of the1,3-diene and the solubility of ethylene in the 1,3-diene at thattemperature and pressure. The pressure of the reactor may range fromabout p.s.i.g. to about 5,000 p.s.i.g., more normally from about 200p.s.i.g. to about 1,000 p.s.i.g., and more preferably less than 1,000p.s.i.g. as 500 p.s.i.g. if no solvent is present.

The molar ratio of reactants include from about l0 to 10 preferably 10-to 10- mols of iron per mol of butadiene-1,3; 0.1 to 10 mols of iron permol of butadiene-1,3; 0.1 to 10 mols of electron donor per mol of iron,preferably 0.25 to 2 mols per mol of iron; and 1 mol of iron to 1 and 10mol equivalents of reducing compound.

It is convenient to carry out the new process in the starting materials(1,3-diene) Without a solvent. If desired to use solvents, suitablesolvents include aliphatic, cycloaliphatic and aromatic hydrocarbons,such as hexane,

4 EXAMPLE V A catalyst solution was prepared by reacting 25.4 grams (0.1mol) of ferrous acetylacetonate, 2.65 grams (0.05 mol) of acrylonitrilewith 75 cc. of triisobutyl aluminum h 1 t b h d b t re 5 in 3 quarts ofisoprene at '10 C. This solution was then g g 2 g g 2 2 5585 a gg gcharged to 10 gallons of isoprene dried with triisobutyl g a z g gi i ig g sglvems are e'mployed aluminum in a IS-gallon reactor. The reactorwas heated y D to 80 C. and pressured with ethylene to 550 p.s.1.g. TheEXAMPLE 1 reaction was run for hours at 80 C. with an average 10ethylene pressure of 500 p.s.i.g. 11 gallons of crude product 10 grams Qllnlhmols) fermus.acety1acet?nate was obtained and was found to contain49% of 4-methyl- 2 grams (2O mlulmls) of trlethylamule were surfed mmcis-l,4-hexadiene and 1% of S-methyl-cis-1,4-hexadiene 3 quarts ofbutad1ene-1,3 whlch was then cooled to -10 (78% based on isopreneconvrted) and of tnlsobutyl alllmmum m 30 of butadl' When this examplewas repeated with diphenylsulfone, me-L3 was adqed thereto Thls catalystsollltlon was then 15 triethylamine, morpholine, and benzonitrile,yields of 59 charged to a sinned 15 'ganon 9 Sontammg 9 gtnms to 78%4-methyland S-methyl-cis-1,4-hexadiene based of dry butad1ene'13 treated1th tmsobutyl alumlmim' on isoprene conversion were obtained. When theseexam- Ethylene was charged to Obtam a pressure of 200 ples are repeatedwith other Group VIII metals, different at room tempefatqre and thereactor was then to results are obtained. With palladium compounds,trans- 600 and mamtamed at 65 for 23 hours Dunng i 2O 1,4-hexadiene isobtained and polymers are obtained reaction, the average pressure ofethylene was 500 p.s.1.g. with cobalt The reactor was vented and 10gallons of product was EXAMPLE VI recovered. This product contained 63%of cis-1,4-hexadiene. The cis-l,4-hexadiene was readily isolated bydistil- 0-324 f m111lIT 101$) 0f feIT1C 611191116 and lation and had apurity of 99+1% 25 gram (1 mrllimol) of tr ethylamme were stirred into150 cc. of butad1ene-1,3 which was then cooled to l0 C. EXAMPLE H and 2cc. of triisobutyl aluminum in 10 cc. butadiene-l,3 The procedure ofExample I was repeated with 0.1 mol was added thefeto- T1115 mlxmre wasthen charged to an of g of .0 eight-sie e:2assassinate; ats; reactedwith 1 cc. 0 triiso uty a uminum. e reaction was run for 23 hours at andthe ethylene pres 20 hours. The resulting product contained 41% ofc1s-1,4- sure was maintained at 500 p.s.i.g. 10 gallons of reactionhexad}ene- The remamdel' was Polymer and Breaded product was obtainedfrom which cis-l,4-hexadiene was butadlene and ethyleneisolated bydistillation in a yield of 66%. EXAMPLE VII EXAMPLE m The procedure ofExample VI was repeated with piper- The rocedure of Example I wasrepeated with a numylene, in place of butadiene, 4 millimols of ferrousacet l- P Y ber of other electron donors. Reaction conditions andacetonate, 0.174 gram (2 millimols of mor holine and o e 0 I P yieldsare set forth in Table 1 below. 0.05 mol of benzomtrrle reacted with 3cc. of triisobut 1 TABLE 1 Average Percent Metalzelectron donor Temp.ethylene Time butadiene Percent Run (mol ratio) 0.) press. (p.s.i.g.)(hrs.) conversion hexadlene (1) Fezl triethylamine 70 575 52 9o 61 2).Fe:% triethylamine s0-140 800 2 94 61 3 Feiyg triethylamine 65 1,700 2396 66 (4) Fe: 1benzonitri1e 80 75 20 98 67 (5) Fez benzonitrile- 65 50018 98 71 (6) Fe: %benzonitrile 80 550 10 98 72 (7) Fe:% benzonitrile 80575 23 97 69 EXAMPLE IV aluminum. The reaction was run for 60 hours atC.,

th The procedure of Example I was repeated with the 55 i fiz i ggfi iigg gg Ob exception that the reactions were conducted in a 3-l1ter E I & 0t d g 3? f f autoclave using additional electron donors. The reaction Ig f g f fi lmols o w e 2 1 :12am...zszazaazz ssssss ow. 0 ya y ene p0yammes, partlcu ar y tria y ene 1- amines containing 2 to 10 carbonatoms are particularly so i ;555 1 21253:3 15 22311 ff fg iff fl t euseful in this reaction. g g m1 5 o TABLE 2 Average PercentMetahelectron donor Temp. ethylene Time butadiene Percent Run (molratro)0.) press. (p.s.i.g.) (hrs.) conversion hexadiene (1) Fe:% morpholine 653,200 18 98 50 (2). Fe:% trlethylenediamine 80 2,700 4 98 50 (3) 85 3,000 20 9s 50 4 80 3,600 47 e0 (5) Fe dlphenylsulione 250 23 94 56 (6)Fe:%triethylamine 250 19 97 58 (7) Fe triethylamine 205 10 95 03 70 55043 0e 02 (9) Fe:% benzonitrile 70 1, 300 20 95 43 diethyl, (2) 10millimols of ethyl magnesium bromide, and (3) 10 millimols oftriisobutyl borane. Excellent yields of cis-1,4-hexadiene were obtainedwith 1) and (2), and acceptable yields with (3).

The cis-l,4-dienes polymerize readily with ethylene and propylene toform sulfur vulcanizable products, One commercial and economic advantageof this process is that polymerization grade butadiene-1,3 and isopreneare not required. Streams from ethylene cracking units which contain1.3-dienes may be used in preparing the cis-1,4-dienes.

I claim:

1. The method for preparing cis-1,4-dienes which comprises reacting a1,3-diene selected from the group consisting of butadiene-l,3, isopreneand piperylene with ethylene in the presence of a catalyst formed byreacting together in the presence of said 1,3-diene, about 10- to 10mols of iron per mol of 1,3-diene of a reducible iron compound selectedfrom the group consisting of an iron salt of an inorganic acid, an ironsalt of an organic acid and an iron chelate with about 1 to 10 molequivalents per mol of iron of an alkyl aluminum compound having thestructure R Al wherein R is an alkyl group containing 1 to 12 carbonatoms; and about 0.1 to 10 mols, per mol of iron, of an organic nitrogencompound selected from the group consisting of acetonitrile,benzonitrile, and polyalkylene polyamines containing 2 to 10 carbonatoms.

References Cited UNITED STATES PATENTS 3,219,716 11/1965 Wittenberg etal 260666 3,244,678 4/1966 Tocker 260-85.3 3,306,948 2/1967 Kealy 2606803,309,418 3/1967 Hata 260680 OTHER REFERENCES Hata, I. Am. Chem. Soc.,vol. 86, p. 3903 (1964). Iwamoto et a1., Bull. Chem. Soc. Japan, vol.39, pp. 2001-2004 (1966).

PAUL M. COUGHLAN, 1a., Primary Examiner.

fg gy UNITED STATES PATENT OFFICE.

CERTIFICATE OF CORRECTION Patent NO- 3 l tl Dated Inv Wolfgang SchneiderIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 69, delete "0.1 to 10 mols of iron per mol of butadi-5column 2, line 70, delete "ene-l,3;".

SIGNED AND SEALED APR 7 1970 (SEAL) Attest:

Edward M. F I mum E. 50mm, JR-

Auesting Officer Commissioner or mums

